I have a brand-new KAN 950 - cycled once on a triton.
I mounted it on my Slow Stik with a GWS 350 and 11x8 prop with an ElectriFly C-10 speed controller. The servos are JR 331 servos. When I go full throttle-up, the rudder servo starts twitching wildly and going crazy.

Formerly, I was using qualcomms on the Slow Stik without any problems.

Could it be that the 11x8 is drawing too many amps through the C-10? I only have 9x7s and I don't think those will work too well.

It is possible you are loading down the system (this includes wires, connectors, etc.) enough that the C-10 can't supply adequate voltage to the radio system. There are other possibilities as well. Start by telling us the cell count.

A loose weld/solder joint. Bad plug connection might cause this. See if putting pressure (twisting and pushing at various places) on the battery while pluged into your plane with Tx and rx on causes the twitching to stop or get worse.

When an ESC's amp limit is exceeded, shouldn't it just shut down? Or SMOKE.... Does it have an overcurrent limiter built in? Check specs -
hoppy

The overload protection just shuts off the motor -
"Battery Eliminator Circuitry provides sufficient current for the
receiver and two micro servos. The motor battery powers the
receiver and servos, then when voltage is reduced to 3.7 v, the low voltage cut-off circuitry stops the motor while continuing to supply power to the receiver and servos. Built-in thermal shutdown protection turns the motor off if the transistors overheat."